1. Field of the Invention
The present invention relates to a plasma display panel, and more particularly, to a structure of a discharge electrode and dielectric layer for a plasma display panel, which reduces discharge current.
2. Background of the Related Art
Generally, a plasma display panel and a liquid crystal display (LCD) have lately attracted considerable attention as the most practical next display of panel displays. In particular, the plasma display panel has higher luminance and wider visible angle than the LCD. For this reason, the plasma display panel is widely used as a thin type large display such as an outdoor advertising tower, a wall TV, and a theater display.
FIG. 1a shows a structure of a related art plasma display panel of three-electrode area discharge type. As shown in FIG. 1a, the plasma display panel of three-electrode area discharge type includes an upper substrate 10 and a lower substrate 20 which are bonded opposite to each other. FIG. 1b shows a sectional structure of the plasma display panel of FIG. 1a, in which the lower substrate 20 is rotated by 90xc2x0.
The upper substrate 10 includes scan electrodes 16 and 16xe2x80x2, sustain electrodes 17 and 17xe2x80x2, a dielectric layer 11, and a passivation film 12. The scan electrodes 16 and 16xe2x80x2 are formed in parallel to the sustain electrodes 17 and 17xe2x80x2. The dielectric layer 11 is deposited on the scan electrodes 16 and 16xe2x80x2 and the sustain electrodes 17 and 17xe2x80x2.
The lower substrate 20 includes an address electrode 22, a dielectric film 21 formed on an entire surface of the substrate including the address electrode 22, an isolation wall 23 formed on the dielectric film 21 between the address electrodes, and a phosphor 24 formed on surfaces of the isolation wall 23 in each discharge cell and the dielectric film 21. Inert gases such as He and Xe are mixed in a space between the upper substrate 10 and the lower substrate 20 at a pressure of 400 to 500 Torr. The space is used as a discharge area.
In general, a mixing gas of Hexe2x80x94Xe is used as the inert gas filled in a discharge area of a DC plasma display panel while a mixing gas of Nexe2x80x94Xe is used as the inert gas filled in a discharge area of an AC plasma display panel.
The scan electrodes 16 and 16xe2x80x2 and the sustain electrodes 17 and 17xe2x80x2 include discharge electrodes 16 and 17 and bus electrodes 16xe2x80x2 and 17xe2x80x2 of metal so as to increase optical transmitivity of each discharge cell, as shown in FIGS. 2a and 2b. FIG. 2a is a plane view of the sustain electrodes 17 and 17xe2x80x2 and the scan electrodes 16 and 16xe2x80x2 and FIG. 2b is a sectional view thereof.
A discharge voltage is applied to the bus electrodes 16xe2x80x2 and 171 from an externally provided driving integrated circuit(IC). The discharge voltage is applied to the discharge electrodes 16 and 17 to generate discharge between the adjacent discharge electrodes 16 and 17. The discharge electrodes 16 and 17 have an overall width of about 300 xcexcm and are made of indium oxide or tin oxide. The bus electrodes 16xe2x80x2 and 17xe2x80x2 are formed of three-layered thin film of Crxe2x80x94Cuxe2x80x94Cr. At this time, the bus electrodes 161 and 171 have a line width of ⅓ of a line width of the discharge electrodes 16 and 17.
FIG. 3 is a wiring diagram of scan electrodes (Smxe2x88x921, Sm, Sm+1, . . . , Snxe2x88x921, Sn, Snn+1) and sustain electrodes (Cmxe2x88x921, Cm, Cm+1, . . . , Cnxe2x88x921, Cn, C+1) arranged on the upper substrate. In FIG. 3, the scan electrodes are insulated from one another while the sustain electrodes are connected in parallel. Particularly, a block indicated by a dotted line in FIG. 3 shows an active area where an image is displayed and the other blocks show inactive areas where an image is not displayed. The scan electrodes arranged in the inactive areas are generally called dummy electrodes 26. The number of the dummy electrodes 26 are not specially limited.
The operation of the aforementioned AC plasma display panel of three-electrode area discharge type will be described with reference to FIGS. 4a to 4d. 
If a driving voltage is applied between the address electrodes and the scan electrodes, opposite discharge occurs between the address electrodes and the scan electrodes as shown in FIG. 4a. The inert gas implanted into the discharge cell is instantaneously excited by the opposite discharge. If the inert gas is again transited to the ground state, ions are generated. The generated ions or some electrons of quasi-excited state come into collision with a surface of the passivation film as shown in FIG. 4b. The collision of the electrons secondarily discharges electrons from the surface of the passivation film. The secondarily discharged electrons come into collision with a plasma gas to diffuse the discharge. If the opposite discharge between the address electrodes and the scan electrodes ends, wall charges having opposite polarities occur on the surface of the passivation film on the respective address electrodes and the scan electrodes.
If the discharge voltages having opposite polarities are continuously applied to the scan electrodes and the sustain electrodes and at the same time the driving voltage applied to the address electrodes is cut off, area discharge occurs in a discharge area on the surfaces of the dielectric layer and the passivation film due to potential difference between the scan electrodes and the sustain electrodes as shown in FIG. 4d. The electrons in the discharge cell come into collision with the inert gas in the discharge cell due to the opposite discharge and the area discharge. As a result, the inert gas in the discharge cell is excited and ultraviolet rays having a wavelength of 147 nm occur in the discharge cell. The ultraviolet rays come into collision with the phosphors surrounding the address electrodes and the isolation wall so that the phosphors are excited. The excited phosphors generate visible light rays, and the visible light rays display an image on a screen.
One pixel includes a discharge cell having a red phosphor, a discharge cell having a green phosphor, and a discharge cell having a blue phosphor. The plasma display panel displays contrast of an image by controlling the number of discharges in each discharge cell.
The related art plasma display panel has several problems.
Since the distance between the discharge areas is short as compared with a general discharge tube display, ultraviolet rays in a positive column area having good emitting efficiency are not generated. In other words, as shown in FIG. 9, since discharge current (2) generated in a discharge electrode spaced apart from a field convergence area is remarkably lower than discharge current (1) generated in a discharge electrode of the field convergence area, in the related art plasma display panel, discharge time is short. As a result, ultraviolet rays are generated in a negative glow area but are not generated in the positive column area. This reduces emitting efficiency and picture quality as compared with the general discharge tube.
Accordingly, the present invention is directed to a plasma display panel that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a plasma display panel in which a structure of a discharge electrode and dielectric layer is provided to generate ultraviolet rays in a positive column area.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a plasma display panel according to the present invention includes: a plurality of first and second bus electrodes successively formed on a substrate at a predetermined interval; a plurality of first discharge electrodes formed with a plurality of first branches branched at a first width for each first bus electrode, a plurality of first centers extended from the first branches to a second width greater than the first width, and a plurality of first ends extended from the first centers to a third width smaller than the second width; a plurality of second discharge electrodes successively branched at a predetermined interval for each second bus electrode and spaced apart from the first ends; and a dielectric layer deposited on areas between the first and second discharge electrodes at a first thickness and on some areas on the first and second discharge electrodes at a second thickness.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.